This invention relates to optoelectronic devices for checking the number of cigarettes (or of any other rod-like articles) forming an orderly group of cigarettes to be packed, and/or the regularity of the cigarette ends, the said devices comprising a box-like cigarette-checking head provided with a plurality of parallel feeler pins which are axially slidably mounted in said head, in an arrangement matching with that of the cigarettes constituting a cigarette group, and the said cigarette-checking head being slightly pressed in a direction parallel to the feeler pins, with its feeler pins abutting against the cigarette ends, so as to resiliently shift back the feeler pins having met a cigarette with a regular end, and to thus remove the corresponding screens that normally prevent the light rays being emitted from suitable sources, such as, for example, light emitting diodes, from falling on photosensitive elements, such as, for example, phototransistors, whereby to achieve an electric condition which is indicative of the regularity of the checked cigarette group; whereas, from a feeler pin being not shifted back, there is derived the absence of the respective cigarette, and/or any irregularity in the cigarette end, and so an electric condition informing of a defect will be generated, that may be used for any desired purpose, such as for discarding later a pack with an incomplete or irregular cigarette group.
In the cigarette-checking devices of the said known type, the tobaco dust is apt to settle down within the box-like head bores in which the feeler pins are guided, thus tending to reduce the slidability of said pins. In an electro-mechanic cigarette-checking device of said known type, in which to each feeler pin is associated an electric contact that, for example, is closed when in rest condition, and is opened any time a feeler pin meets a cigarette, so that this pin will be resiliently shifted thereby, inwardly of the cigarette-checking head, or vice-versa, in order to guarantee the slidability of the feeler pins and to prevent any tobacco dust from penetrating into the hollow space in the cigarette-checking head and marring the electric contacts, air under pressure is fed into the said hollow space and is caused to flow out through the annular gaps between the feeler pins and the walls of the feeler pin-guiding bores in the cigarette-checking head, so that the said air under pressure will remove the tobacco dust tending to accumulate in said gaps. However, this arrangement is hardly applicable to the optoelectronic cigarette-checking devices of the type as disclosed in the preamble, or anyhow, it proves to be unsufficient for guaranteeing a satisfactory operation of these devices, since the inner dust resulting from the wear of the feeler pin-sliding surfaces, tends to settle down on the photosensitive elements and on the light sources, thus very shortly reducing or quite destroying their efficiency.
The object of the invention is to eliminate the aforementioned drawbacks, and to guarantee, in the optoelectronic cigarette-checking devices of the type as disclosed in the preamble, both the slidability of the feeler pins and a clean condition of the photosensitive elements and the light sources, simply by means of air under pressure.
This problem is solved by the invention thanks to the provision of means for feeding air under pressure into the hollow space in the box-like cigarette-checking head, so as to cause it to first sweep the photosensitive elements and/or the light sources. In this way, the air under pressure fed into the hollow space in the box-like cigarette-checking head will at first remove from the surfaces of the photosensitive elements and the light sources which are swept thereby, the dust deposit formed by any dust possibly existing in the interior of said head, whereby the said surface will be kept dust-free, and therefore always in a thoroughly efficient condition, and the said air under pressure will then flow out of the box-like cigarette-checking head, through the annular gaps between the feeler pins and the guides provided for the sliding thereof in the cigarette-checking head, thus removing from said gaps any tobacco dust, and guaranteeing the slidability of the feeler pins.